Behavioral and endocrine influences have been investigated in the induction and maintenance of sexual behavior in the female golden hamster (MESOCRICETUS AURATUS). Behavioral receptivity was induced by estradiol (1 ug or more) followed in 48 hours by progesterone (50 ug or more), or by long-term (6 days or more) treatment with estradiol, which produced a submaximal receptivity. In unmated females estradiol and progesterone- induced receptivity lasted 12 to 18 hours, after which partial receptivity was apparent for as long as the hormones were continued (at least several weeks). Following mating (i.e. in mated females) sexual receptivity was almost totally attenuated within 2 to 6 hours, and mated females remained unresponsive to further hormones for a period of at least 17 days, or for as long as progesterone remained in the system. Females treated only with estradiol showed short-term effects of mating but recovered responsivity within one to three days. Progesterone has, therefore, been implicated in the long-term inhibitory effects of mating. Neither adrenal nor pituitary hormones are essential for the induction of receptivity (following exogenous estradiol or progesterone) nor for either long or short-term effects of mating to be apparent. Serotonin has, however, been implicated in the short-term inhibitory effects of mating on subsequent sexual behavior. Current studies are examining the pharmacological correlates of female behavior and also the possible effects of hypothalamic releasing hormones on sexual receptivity in this species.